WHYDUNIT French’s third novel is her best, its crime story emerging from precise characterization and a detailed family saga.

Faithful Place | By Tana French | 432 pages | Random House | $25.95

Frank Mackey's life changed when he was 19. The year was 1985, and he and his girlfriend Rosie Daly were about to run away together. Growing up in Faithful Place, one of working-class Dublin's more depressed byways, they knew they had no future in Ireland, particularly because Rosie's aspiring family despised Frank's booze-ruined clan. London — freedom — beckoned, and they were making their break.

Except that Rosie never showed, and the letter Frank found made it seem she shared her parents' aversion to his violent, alcoholic family. So he went off alone, hating everyone who'd doomed him to a lonely, loveless life.

Twenty-two years later and Frank Mackey is still in Dublin, though he's never returned to the old neighborhood. Now he's on the Undercover Squad, with a beautiful daughter, an educated ex-wife, and the kind of life nobody in Faithful Place could ever imagine. His only contact with the past is through one sister, Jackie. And so, when she calls to say that Rosie's suitcase has been found in the abandoned house where the lovers used to meet, the complications are not only criminal, they're personal, as Frank's past rises up to meet him with a vengeance.

Frank, who played a minor role as the tough boss in Tana French's second mystery, The Likeness, is both the star and the victim in the Dublin-based author's gorgeous third work. Like its predecessors, this mystery has a vivid sense of a place that has shaped its people. "The area wasn't dodgy exactly," she writes in Frank's voice, "just separate," with a code that specified that "you leave the heroin to them down in the flats" and "even if you're an anarchist punk rocker this month, you go to Mass on Sunday." Of course, the final part of that code, as in tough neighborhoods everywhere, was always that "you never, ever squeal on anyone." Which makes Frank's return as an officer of the law problematic.

The people of Faithful Place are depicted with an equally deft shorthand that sets the stage for everything to follow. "My da started off as a plasterer, but by the time we came along he was a full-time drinker with a part-time sideline in things that had fallen off the backs of lorries." It's a slag, as nasty as it is true, but that thumbnail will come back later to explain a crucial conflict. Such sketches also show the passage of time, as when Rosie and her friends, "a sweet giggly bubble of flowery smells and big hair and glittery lip gloss" in 1985, age, one becoming "mammy shaped . . . with mammy hair to match" while another has "kept her figure" but been much less fortunate otherwise. "She had a hand pressed over her mouth," Frank notes. "Someone had trained her not to scream."